Substrate for liquid crystal display, liquid crystal display having the same and method of manufacturing the same

ABSTRACT

It is an object of the invention to provide a substrate for a liquid crystal display, a liquid crystal display having the same, and a method of manufacturing the same which make it possible to provide a display having high luminance and preferable display characteristics to be used in display sections of information apparatuses and the like. Each pixel is defined by gate bus lines extending in the horizontal direction and drain bus lines extending in the vertical direction. TFTs are formed in the vicinity of intersections between the bus lines, and resin overlap sections for shielding the TFTs from light are formed above the same. No black matrix is formed on a common electrode substrate which is provided in a face-to-face relationship with a TFT substrate, and the bus lines and the resin overlap sections formed on the TFT substrate function as a black matrix.

This is a divisional of application Ser. No. 10/166,119, filed Jun. 10,2002 now U.S. Pat. No. 7,145,619.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display substrate thatforms a part of a liquid crystal display used in a display section of aninformation apparatus or the like, a liquid crystal display having thesame and a method of manufacturing the same.

2. Description of the Related Art

In general, a liquid crystal display comprises two substrates having atransparent electrode and a liquid crystal sealed between the twosubstrates. The liquid crystal is driven by applying a voltage betweenthe two transparent electrodes to control the transmittance of lightthrough the liquid crystal, which allows a desired image to bedisplayed. An active matrix liquid crystal display is comprised of a TFTsubstrate having thin film transistors (TFTs) for switching respectivepixels formed thereon and a common electrode substrate having a commonelectrode formed thereon. A recent increase in the need for liquidcrystal displays has resulted in diverse requirements for liquid crystaldisplays. In particular, there are strong demands for improvements ofviewing angle characteristics and display quality, and VA (verticallyaligned) mode liquid crystal displays are regarded as promising meansfor satisfying such demands.

A VA mode liquid crystal display is comprised of two substrates whichhave been subjected to a vertically aligning process on surfaces thereoffacing each other and a liquid crystal having negative dielectricanisotropy sealed between the two substrates. The liquid crystalmolecules of the liquid crystal are characterized by homeotropicalignment and are aligned substantially perpendicularly to the substratesurfaces when no voltage is applied between the electrodes. They arealigned substantially in parallel with the substrate surfaces when apredetermined voltage is applied between the electrodes and are alignedat an angle to the substrate surfaces when a voltage lower than saidvoltage is applied.

MVA (multi-domain vertical alignment) type liquid crystal displays arerecently attracting attention from the viewpoint of improvement ofviewing angle characteristics of liquid crystal displays. In the case ofan MVA type display, a pixel is divided into a plurality of domainsusing alignment regulating structures such as linear protrusions andslits provided on two substrates to achieve separate alignment in whichliquid crystal molecules are tilted in a different direction in eachdomain.

FIG. 35 shows a configuration of an MVA type liquid crystal display andshows an arrangement of linear protrusion formed as alignment regulatingstructures on two substrates. FIG. 35 shows three pixels in red (R),green (G) and blue (B). As shown in FIG. 35, linear protrusions 104 areformed on a TFT substrate 108 and linear protrusions 106 are formed on acommon electrode substrate 110. The linear protrusions 104 and 106 areformed at an angle to the pixels. Each of the R, G and B pixel regionsis defined by a black matrix (BM) 102 formed on the common electrodesubstrate 110. The BM 102 serves as a light shield for a storagecapacity bus line extending across each pixel substantially in themiddle thereof and a storage capacity electrode located above the same(both of which are not shown).

FIG. 36 is a sectional view of the liquid crystal display taken alongthe line X-X in FIG. 35. As shown in FIG. 36, the TFT substrate 108 hasa pixel electrode 114 formed for each pixel on a glass substrate 112.The figure omits an insulation film, drain bus lines, a protective film,and soon formed on the glass substrate 112. The linear protrusions 104are formed on the pixel electrodes 114. A vertical alignment film 116 isformed to cover the pixel electrodes 114 and linear protrusions 104entirely. The common electrode substrate 110 has the BM 102 formed onthe glass substrate 112. Resin color filter (CF) layers R, G and B (FIG.36 shows the filters G and B only) are formed in each of the pixelregions defined by the BM 102 on the glass substrate 112. A commonelectrode 118 is formed on the region CF layers R, G and B, and thelinear protrusions 106 are formed on the common electrode 118. Further,a vertical alignment film 116 is formed to cover the common electrode118 and linear protrusions 106 entirely. Spherical spacers 122 made ofplastic or glass for maintaining a gap (cell gap) between the substrates108 and 110 and a liquid crystal LC is sealed between the TFT substrate108 and common electrode substrate 110.

FIG. 37 is a sectional view of the liquid crystal display taken alongthe line Y-Y in FIG. 35, and it shows a state of the liquid crystal LCwhen no voltage is applied. As shown in FIG. 37, liquid crystalmolecules (represented by columns in the figure) are alignedsubstantially perpendicularly to the vertical alignment films 116 on thetwo substrates 108 and 110. Therefore, liquid crystal molecules in theregions where the linear protrusions 104 and 106 are formed are alignedsubstantially perpendicularly to the surface of the linear protrusions104 and 106 and are aligned at a slight angle to the normal of the twosubstrates 108 and 110. Since polarizers (not shown) are provided in acrossed Nicols configuration outside the two substrates 108 and 110,black display is achieved when no voltage is applied.

FIG. 38 is a sectional view of the liquid crystal display taken alongthe line Y-Y in FIG. 35 similarly to FIG. 37, and it shows a state ofthe liquid crystal LC when a voltage is applied. The broken lines in thefigure represent lines of electric force between the pixel electrodes114 and common electrode 118. As shown in FIG. 38, when a voltage isapplied between the pixel electrodes 114 and common electrode 118, theelectric field is distorted in the vicinity of the linear protrusions104 and 106 which are made of a dielectric material. As a result, thetilting angles of liquid crystal molecules having negative dielectricanisotropy are regulated, and the tilting angles can be controlleddepending on the field intensity to display gray shades.

At this time, if the linear protrusions 104 and 106 are provided inlinear configurations as shown in FIG. 35, liquid crystal molecules inthe vicinity of the linear protrusions 104 and 106 are tilted in twodirections which are orthogonal to the extending directions of thelinear protrusions 104 and 106, the tilting directions beingsymmetrically defined about the linear protrusions 104 and 106. Sincethe liquid crystal molecules in the vicinity of the linear protrusions104 and 106 are at a slight angle to a direction perpendicular to thetwo substrates 108 and 110 even when no voltage is applied, they arequickly tilted in response to the field intensity. The tiltingdirections of liquid crystal molecules in the neighborhood aresequentially determined in accordance with the behavior of theabove-mentioned liquid crystal molecules, and the tilting angles dependon the field intensity. As a result, alignment separation is achieved atthe linear protrusions 104 and 106.

FIG. 39 is a sectional view taken along a line Y-Y of a liquid crystaldisplay as shown in FIG. 35 in which slits 120 are formed in place ofthe linear protrusions 104, the figure showing a state of the displaywhen no voltage is applied. As shown in FIG. 39, the slits 120 which arealignment regulating structures are formed by removing the pixelelectrodes 114. Liquid crystal molecules are aligned substantiallyperpendicularly to the vertical alignment films 116 on the twosubstrates 108 and 110 similarly to the liquid crystal molecules shownin FIG. 37.

FIG. 40 is a sectional view of the liquid crystal display taken alongthe line Y-Y similarly to FIG. 39, and it shows a state of a liquidcrystal LC when a voltage is applied. As shown in FIG. 40, lines ofelectric force substantially similar to those in the regions where thelinear protrusions 104 are formed as shown in FIG. 38 are formed in theregions where the slits 120 are formed. As a result, alignmentseparation is achieved about the linear protrusions 106 and slits 120.FIGS. 37 and 40 omit the spherical spacers 122 for maintaining a cellgap.

FIG. 41 is a sectional view of the liquid crystal display taken alongthe line Z-Z in FIG. 35 showing the neighborhood of a drain bus line126. As shown in FIG. 41, the TFT substrate 108 has an insulation film124 covering an entire surface of the glass substrate 112. The drain busline 126 is formed on the insulation film 124. A protective film 128 isformed on the entire surface of the drain bus line 126. A pixelelectrode 114 for each pixel is formed on the protective film 128. Ablack matrix BM 102 is formed on a common electrode substrate 110provided in a face-to-face relationship with the TFT substrate 108 suchthat it serves as a light shield for regions on the TFT substrate 108where no pixel electrode 114 is formed (edges of pixel regions).

The conventional MVA type liquid crystal display has the problem ofdarkness of display because of low transmittance of the panel. The lowpanel transmittance is attributable to various factors including areduction in the numerical aperture caused by misalignment between theTFT substrate 108 and common electrode substrate 110, a reduction in thenumerical aperture attributable to the alignment regulating structures(the linear protrusions 104 and 106 or slits 120), and irregularities inthe alignment of the liquid crystal in the vicinity of the sphericalspacers 122.

Because of significantly improved viewing angle characteristics, MVAtype liquid crystal displays are preferably used as monitors forpersonal computers and the like for which high luminance has relativelylow importance. However, in order to use them as display sections of DVD(digital versatile disk) players or televisions for which high luminanceis an important requirement, it is necessary to provide a brighterback-light or to use a special sheet for aligning light-emittingdirections to improve luminance in a particular direction. This hasresulted in the problem of an increase in the manufacturing cost.

Further, the formation of linear protrusions, an insulation layer, andso on as alignment regulating structures increases manufacturing stepswhen compared to manufacturing steps for normal substrates, whichalso-results in an increase in the manufacturing cost.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a substrate for a liquidcrystal display with which a display having high luminance andpreferable display characteristics can be obtained, a liquid crystaldisplay having the same, and a method for manufacturing the same.

The above-described object is achieved by a liquid crystal displaysubstrate, characterized in that it comprises a substrate whichsandwiches a liquid crystal having negative dielectric anisotropy incombination with an opposite substrate provided in a face-to-facerelationship, a plurality of gate bus lines formed on the substrate, aplurality of drain bus lines formed on the substrate such that theyintersect the gate bus lines, pixel regions defined by the gate buslines and the drain bus lines, a thin film transistor formed in each ofthe pixel regions, a resin color filter layer formed in each of thepixel regions, a pixel electrode formed in each of the pixel regions,and an alignment regulating structure formed on the substrate forregulating the alignment of the liquid crystal.

The above-described object is achieved by a liquid crystal display,characterized in that it comprises: a thin film transistor substrateincluding a first substrate, a plurality of bus lines formed on thefirst substrate such that they intersect each other, pixel regionsdefined by the bus lines, a thin film transistor formed in each of thepixel regions, a resin color filter layer formed in each of the pixelregions, and a pixel electrode formed in each of the pixel regions; acommon electrode substrate including a second substrate different fromthe first substrate in the thickness or material and a common electrodeformed on the second substrate, the common electrode substrate beingprovided in a face-to-face relationship with the first substrate; and aliquid crystal sealed between the thin film transistor substrate and thecommon electrode substrate.

Further, the above-described object is achieved by a liquid crystaldisplay substrate, characterized in that it comprises a substrate whichsandwiches a liquid crystal in combination with an opposite substrateprovided in a face-to-face relationship therewith, a plurality of gatebus lines formed on the substrate, a plurality of drain bus lines formedon the substrate such that they intersect the gate bus lines, pixelregions defined by the gate bus lines and the drain bus lines, a thinfilm transistor formed in each of the pixel regions, a resin colorfilter layer formed in each of the pixel regions, a pixel electrodeformed in each of the pixel regions, and a resin layer formed to coversource and drain electrodes of the thin film transistor and the drainbus lines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of a liquid crystal display in a first modefor carrying out the invention;

FIG. 2 is a sectional view showing a first basic configuration of asubstrate for a liquid crystal display in the first mode for carryingout the invention, a liquid crystal display having the same, and amethod of manufacturing the same;

FIG. 3 is a sectional view showing a modification of the first basicconfiguration of a substrate for a liquid crystal display in the firstmode for carrying out the invention, a liquid crystal display having thesame, and a method of manufacturing the same;

FIG. 4 is a sectional view showing a second basic configuration of asubstrate for a liquid crystal display in the first mode for carryingout the invention, a liquid crystal display having the same, and amethod of manufacturing the same;

FIG. 5 shows a third basic configuration of a substrate for a liquidcrystal display in the first mode for carrying out the invention;

FIGS. 6A and 6B show the third basic configuration of a substrate for aliquid crystal display in the first mode for carrying out the invention;

FIG. 7 shows a configuration of a liquid crystal display according toEmbodiment 1-1 in the first mode for carrying out the invention;

FIG. 8 is a sectional view showing a configuration of a substrate for aliquid crystal display according to Embodiment 1-1 in the first mode forcarrying out the invention;

FIG. 9 shows a configuration of a substrate for a liquid crystal displayaccording to Embodiment 1-1 in the first mode for carrying out theinvention;

FIGS. 10A and 10B are sectional views showing the configuration of thesubstrate for a liquid crystal display according to Embodiment 1-1 inthe first mode for carrying out the invention;

FIGS. 11A and 11B are sectional views taken at a manufacturing stepshowing a method of manufacturing the substrate for a liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIGS. 12A and 12B are sectional views taken at a manufacturing stepshowing the method of manufacturing the substrate for a liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIGS. 13A and 13B are sectional views taken at a manufacturing stepshowing the method of manufacturing the substrate for a liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIGS. 14A and 14B are sectional views taken at a manufacturing stepshowing the method of manufacturing the substrate for a liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIGS. 15A and 15B are sectional views taken at a manufacturing stepshowing the method of manufacturing the substrate for a liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIGS. 16A and 16B are sectional views taken at a manufacturing stepshowing the method of manufacturing the substrate for a liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIG. 17 is a sectional view showing a configuration of a liquid crystaldisplay according to Embodiment 1-2 in the first mode for carrying outthe invention;

FIG. 18 is a sectional view showing the configuration of the liquidcrystal display according to Embodiment 1-2 in the first mode forcarrying out the invention;

FIG. 19 shows a configuration of a substrate for a liquid crystaldisplay according to Embodiment 1-3 in the first mode for carrying outthe invention;

FIG. 20 is a sectional view showing the configuration of the substratefor a liquid crystal display according to Embodiment 1-3 in the firstmode for carrying out the invention;

FIG. 21 is a sectional view taken at a manufacturing step showing amethod of manufacturing the substrate for a liquid crystal displayaccording to Embodiment 1-3 in the first mode for carrying out theinvention;

FIG. 22 is a sectional view taken at a manufacturing step showing themethod of manufacturing the substrate for a liquid crystal displayaccording to Embodiment 1-3 in the first mode for carrying out theinvention;

FIG. 23 shows a configuration of a substrate for a liquid crystaldisplay according to Embodiment 2-1 in a second mode for carrying outthe invention;

FIG. 24 is a sectional view taken at a manufacturing step showing aconfiguration of a liquid crystal display according to Embodiment 2-2 inthe second mode for carrying out the invention;

FIG. 25 shows a configuration of a liquid crystal display according toEmbodiment 3-1 in a third mode for carrying out the invention;

FIGS. 26A and 26B are sectional views showing the configuration of theliquid crystal display according to Embodiment 3-1 in the third mode forcarrying out the invention;

FIG. 27 shows a method of manufacturing the liquid crystal displayaccording to Embodiment 3-1 in the third mode for carrying out theinvention;

FIG. 28 shows the method of manufacturing the liquid crystal displayaccording to Embodiment 3-1 in the third mode for carrying out theinvention;

FIG. 29 shows the method of manufacturing the liquid crystal displayaccording to Embodiment 3-1 in the third mode for carrying out theinvention;

FIG. 30 shows the method of manufacturing the liquid crystal displayaccording to Embodiment 3-1 in the third mode for carrying out theinvention;

FIGS. 31A and 31B are sectional views taken at a manufacturing stepshowing the method of manufacturing the liquid crystal display accordingto Embodiment 3-1 in the third mode for carrying out the invention;

FIGS. 32A and 32B are sectional views taken at a manufacturing stepshowing the method of manufacturing the liquid crystal display accordingto Embodiment 3-1 in the third mode for carrying out the invention;

FIGS. 33A and 33B are sectional views taken at a manufacturing stepshowing the method of manufacturing the liquid crystal display accordingto Embodiment 3-1 in the third mode for carrying out the invention;

FIGS. 34A and 34B are sectional views showing a configuration of aliquid crystal display according to Embodiment 3-2 in the third mode forcarrying out the invention;

FIG. 35 shows a configuration of a conventional liquid crystal display;

FIG. 36 is a sectional view showing the configuration of theconventional liquid crystal display;

FIG. 37 is a sectional view showing the configuration of theconventional liquid crystal display;

FIG. 38 is a sectional view showing the configuration of theconventional liquid crystal display;

FIG. 39 is a sectional view showing the configuration of theconventional liquid crystal display;

FIG. 40 is a sectional view showing the configuration of theconventional liquid crystal display;

FIG. 41 is a sectional view showing the configuration of theconventional liquid crystal display; and

FIG. 42 is a sectional view showing a modification of the substrate fora liquid crystal display according to Embodiment 1-2 in the first modefor carrying out the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Mode forCarrying Out the Invention

A description will be made with reference to FIGS. 1 through 22 and FIG.42 on a substrate for a liquid crystal display in a first mode forcarrying out the invention, a liquid crystal display having the same,and a method of manufacturing the same. A first basic configuration inthe present mode for carrying out the invention will be described withreference to FIGS. 1 and 2. FIG. 1 shows three pixels in R, G and B on aTFT substrate 8. As shown in FIG. 1, the pixels are defined by gate buslines 25 extending in the horizontal direction in the figure and drainbus lines 26 extending in the vertical direction in the figure. TFTs (noshown) are formed in the vicinity of intersections between the bus lines25 and 26. Above the TFTs, in order to prevent light from impinging uponthe TFTS, resin overlap sections 32 are formed in which at least two outof resin CF layers R, G and B are overlapped with each other. In theliquid crystal display in the present mode for carrying out theinvention, no black matrix is formed on a common electrode substratewhich is provided in a face-to-face relationship with the TFT substrate8, and the bus lines 25 and 26 and the resin overlap sections 32 formedon the TFT substrate 8 provides the function of a black matrix. Lightcan be blocked by forming any one of the resin CF layers R, G and B onthe TFTs instead of the resin overlap sections 32 shown in FIG. 1.

FIG. 2 is an illustration showing a first basic configuration of asubstrate for a liquid crystal display in the present mode for carryingout the invention and a liquid crystal display having the same is asectional view of the liquid crystal display taken along the line A-A inFIG. 1. As shown in FIG. 2, the TFT substrate 8 has an insulation film24 formed on a substantially entire surface of a glass substrate 12. Thedrain bus lines 26 are formed on the insulation film 24. The resin CFlayers R, G and B (FIG. 2 shows the layers G and B only) are formed onthe drain bus lines 26 (a CF-on-TFT structure). A pixel electrode 14 foreach pixel is formed on the resin CF layers R, G and B. A commonelectrode substrate 10 provided in a face-to-face relationship with theTFT substrate 8 is comprised of a glass substrate 12 and a commonelectrode 18 formed on an entire surface thereof. No black matrix isformed on the common electrode substrate 10. A vertical alignment film(not shown) is formed to cover the pixel electrode 14 and commonelectrode 18 entirely. A liquid crystal layer LC is sealed between theTFT substrate 8 and common electrode substrate 10.

In the conventional liquid crystal display shown in FIG. 41, a capacityis formed between the pixel electrode 114 and drain bus line 126 withthe protective film 128 sandwiched as a dielectric material if the pixelelectrode 114 is formed such that it extends above the drain bus line126. It is therefore necessary to provide a predetermined gap extendingin parallel with the substrate surface between the pixel electrode 114and drain bus line 126.

On the contrary, in the liquid crystal display in the present mode forcarrying out the invention shown in FIG. 2, the resin CF layers R, G andB are formed between the pixel electrodes 114 and drain bus lines 126.Since the resin CF layers R, G and B are applied and formed using a spincoat process or the like, they can be easily formed with a greatthickness compared to the protective film 128 that is formed using a CVD(chemical vapor deposition) process. It is therefore possible to reduceany electrostatic capacity generated between the drain bus lines 26 andpixel electrodes 14. Since this makes it possible to form the pixelelectrodes 14 in an overlapping relationship with the drain bus lines 26in the direction perpendicular to the substrate surface, there is noneed for forming a black matrix on the common electrode substrate 10,which improves the numerical aperture. Further, since the drain buslines 26 serve as a black matrix to eliminate any need for providing ablack matrix on the common electrode substrate 10, the number ofmanufacturing steps is reduced. This also eliminates any reduction inthe numerical aperture attributable to misalignment between the TFTsubstrate 8 and common electrode substrate 10.

The CF-on-TFT structure shown in FIG. 2 is suitable for a TN normallywhite mode liquid crystal display in which leakage of light can occurwhen black is displayed unless pixel electrodes 14 are formed such thatedges of the same overlap drain bus lines 26. However, in order tosuppress a capacity formed in a region where a pixel electrode 14 and adrain bus line 26 overlap each other, the resin CF layers R, G and Bmust be formed with a considerably great thickness. This results in aproblem in that the CF-on-TFT structure necessitates a manufacturingprocess that is more complicated than forming the resin CF layers R, Gand B on the opposite substrate. Further, in order to block light withthe drain bus lines 26 reliably (bus line light-blocking), the resin CFlayers R, G and B must be formed such that their edges are accuratelyaligned with the drain bus lines 26. Therefore, in the case of drain buslines with a very small line width, a proximity exposure apparatus whichis normally used for forming the resin CF layers R, G and B may fail toachieve sufficient alignment. On the contrary, the use of a stepper ormirror-projection type aligner having excellent aligning accuracy canresult in an increase in the manufacturing cost of the CF-on-TFTstructure.

FIG. 3 shows a modification of the first basic configuration shown inFIG. 2. As shown in FIG. 3, the pixel electrodes 14 are formed such thatpredetermined gaps in the direction of the substrate surface are keptbetween edges of the pixel electrodes 14 and drain bus line 26 in orderto prevent the pixel electrodes 14 from overlapping the drain bus line26 when viewed in the direction perpendicular to the substrate surface.An edge of the resin CF layer G is formed on the drain bus line 26,however, an edge of the resin CF layer B is misaligned with the top ofthe drain bus line 26 because of a shift during patterning. However, inthe case of a MVA type normally black mode liquid crystal display whichdisplays black when no voltage is applied, even if a pixel electrode 14is formed with a predetermined gap from a drain bus line 26 such thatthey do not overlap each other, the problem of leakage light will notoccur because such a gap region appears in black when no voltage isapplied. Further, since no capacity is generated because no overlapregion is formed between the pixel electrode 14 and drain bus line 26,resin CF layers R, G and B can be as thin as desired. Even when theresin CF layers R, G and B are formed such that their edges aremisaligned with the top of the drain bus line 26 as shown in FIG. 3, nolight leaks as long as the edges of the resin CF layers R, G and B arecloser to the drain bus line 26 than the edges of the pixel electrodes14. Since this makes it possible to provide a great margin for alignmentduring the patterning of the resin CF layers R, G and B, the CF-on-TFTstructure can be obtained at a low cost using a normal proximityexposure apparatus.

FIG. 4 shows a second basic configuration of the substrate for a liquidcrystal display in the present mode for carrying out the invention andthe liquid crystal display having the same, FIG. 4 showing a sectionalview of the liquid crystal display taken along the line B-B in FIG. 1.As shown in FIG. 4, the liquid crystal display has linear protrusions 28as alignment regulating structures formed on the pixel electrodes 14.The resin CF layers R, B and G are laminated in the same order in thevicinity of the intersection between the gate bus line 25 and drain busline 26 to form a resin overlap section 32 to serve as a black matrix. Aprotrusion 29 which does not function as an alignment regulatingstructure is formed on the resin overlap section 32. The protrusion 29is formed simultaneously with the linear protrusions 28 from the samematerial as that of the latter. The resin overlap section 32 between theresin layers forming a part of the TFT substrate 8 and the protrusion 29are laminated to form a columnar spacer 30 which maintains a call gapbetween the TFT substrate and the common electrode substrate 10 providedin a face-to-face relationship.

In the second configuration in the present mode for carrying out theinvention, the columnar spacer is formed by laminating the resin CFlayers and so on forming a part of the TFT substrate 8. Since thisreduces the number of manufacturing steps, the manufacturing cost can bereduced. Further, since this makes it possible to reduce leakage oflight and irregularities of alignment that can occur in the vicinity ofdispersed spacers having a spherical configuration or the like,preferable display characteristics can be achieved.

FIG. 5 shows a third configuration of the substrate for a liquid crystaldisplay in the present mode for carrying out the invention. A framepattern 34 for, shielding edges of a display area 38 from light isformed in a frame region 40 of the common electrode substrate 10. Forexample, a cross-shaped alignment mark used for combining the samesubstrate with the TFT substrate 8 (which is not shown in FIGS. 5 and6B) in a face-to-face relationship is formed outside the frame region40.

FIG. 6A is an enlarged view of the region a of the common electrodesubstrate 10 shown in FIG. 5. FIG. 6B shows a section of the commonelectrode substrate 10 taken along the line C-C in FIG. 6A. As shown inFIGS. 6A and 6B, a common electrode 18 is formed in the display area 38on the glass substrate 12 and in the frame region 40 at the edges of thedisplay area 38. Linear protrusions 28 are formed on the commonelectrode 18 in the display area 38 at an angle to an edge of thedisplay area 38 using a black resist (black resin) or the like. A framepattern 34 for shielding the edges of the display area 38 from light isformed on the common electrode 18 in the frame region 40 simultaneouslywith the linear protrusions 28 from the same material. An alignment mark36 is formed simultaneously with the linear protrusions 28 from the samematerial on the left side of the frame region 40 in the figures.

In the third basic configuration in the present mode for carrying outthe invention, since the: frame pattern 34 and alignment mark 36 areformed simultaneously with alignment regulating structures from the samematerial, the number of steps for manufacturing the common electrodesubstrate 10 is reduced to allow a reduction in the manufacturing cost.

The substrate for a liquid crystal display in the present mode forcarrying out the invention and the liquid crystal display having thesame will now be more specifically described with reference toEmbodiments 1-1, 1-2 and 1-3.

Embodiment 1-1

A description will now be made with reference to FIGS. 7 through 16B ona substrate for a liquid crystal display according to Embodiment 1-1, aliquid crystal display having the same, and a method of manufacturingthe same. FIG. 7 is a conceptual illustration showing a TFT substrate 8and a common electrode substrate 10 which are combined, FIG. 7 showingthree pixels in R, G and B. For example, the liquid crystal display ofthe present embodiment is an MVA type liquid crystal display, and FIG. 7also shows the positions of alignment regulating structures. Linearprotrusions 28 are formed on the common electrode substrate 10 at anangle to edges of the pixel regions. On the TFT substrate 8, slits 20and finer slits 21 extending from the slits 20 substantiallyperpendicularly to the extending direction of the slits 20 are formed atan angle to the edges of the pixel regions. A plurality of finer slits21 are formed at intervals smaller than the intervals between the slits20 and linear protrusions 28. When alignment regulating structures areformed at relatively small intervals, liquid crystal molecules havingnegative dielectric anisotropy are aligned in parallel with thedirection in which the alignment regulating structures extend.Therefore, the alignment of liquid crystal molecules is more stronglyregulated by forming the finer slits 21 perpendicular to the slits 20.

FIG. 8 shows a section of the liquid crystal display taken along theline D-D in FIG. 7. As shown in FIG. 8, the TFT substrate 8 has aninsulation film 24 formed on an entire surface of a glass substrate 12.Drain bus lines 26 are formed on the insulation film 24. Resin CF layersR, G and B (FIG. 8 shows the layers G and B only) are formed on thedrain bus lines 26. Pixel electrodes 14 and the slits 20 which arecuts-off in a part of the pixel electrodes 14 are formed on the resin CFlayers R, G and B. FIG. 8 omits the finer slits 21. The common electrodesubstrate 10 has a common electrode 18 formed on an entire surface of aglass substrate 12. Linear protrusions 28 are formed on the commonelectrode 18. A vertical alignment film (not shown) is formed on thepixel electrodes 14, common electrode 18, and linear protrusions 28. Aliquid crystal LC having negative dielectric anisotropy is sealedbetween the TFT substrate 8 and common electrode substrate 10.

FIG. 9 shows a configuration in the vicinity of TFTs on the TFTsubstrate 8 of the present embodiment. As shown in FIG. 9, the TFTsubstrate 8 has a plurality of gate bus lines 25 (FIG. 9 shows only oneof them) extending in the horizontal direction in the figure and theplurality of drain bus lines 26 (FIG. 9 shows three lines) extending inthe vertical direction in the figure across the gate bus lines 25 on aglass substrate 12. TFTs 42 are formed in the vicinity of intersectionsbetween the bus lines 25 and 26. A TFT 42 is comprised of a drainelectrode 44 that is a branch of a drain bus line 26, a source electrode46 provided in a face-to-face relationship with the drain electrode 44with a predetermined gap kept between them, and a part (gate electrode)of a gate bus line 25 which overlaps the drain electrode 44 and sourceelectrode 46. An active semiconductor layer 52 is formed on the gateelectrode, and a channel protection film 48 is formed on the same. Thegate bus lines 25 and drain bus lines 26 define pixel regions, and resinCF layers R, G and B are formed in each of the pixel regions. A pixelelectrode 14 is formed in each of the pixel regions. The pixelelectrodes 14 are formed such that their edges in the horizontaldirection in the figure overlap edges of the drain bus lines 26 whenviewed in the direction perpendicular to the substrate surfaces. FIG. 9omits slits.

FIG. 10A shows a section of the TFT substrate 8 taken along the line E-Ein FIG. 9, and FIG. 10B shows a section of the TFT substrate 8 takenalong the line F-F in FIG. 9. As shown in FIGS. 10A and 10B, the resinCF layers, R, G and B are formed on the TFTs 42 and drain bus lines 26.The pixel electrodes 14 are formed on the resin CF layers R, G and B.The pixel electrodes 14 are formed such that their edges overlap theedges of the drain bus lines 26 when viewed in the directionperpendicular to the substrate surfaces.

A method of manufacturing the liquid crystal display of the presentembodiment will now be described with reference to FIGS. 11A through16B. FIGS. 11A through 16B are sectional views taken at manufacturingsteps showing the method of manufacturing the liquid crystal display ofthe present embodiment. FIGS. 11A, 12A, 13A, 14A, 15A and 16A show thesection of the TFT substrate 8 taken along the line E-E in FIG. 9, andFIGS. 11B, 12B, 13B, 14B, 15B and 16B show the section of the TFTsubstrate 8 taken along the line F-F in FIG. 9. For example, as shown inFIGS. 11A and 11B, an aluminum (Al) layer having a thickness of 100 nmand a titanium (Ti) layer having a thickness of 50 nm are formed in thesame order on an entire surface of a glass substrate 12 and arepatterned to form gate bus lines 25. The patterning is carried out usinga photolithographic process in which a predetermined resist pattern isformed on the layers to be patterned; the layers to be patterned areetched using the resist pattern as an etching mask; and the resistpattern is then removed.

Next, for example, a silicon nitride film (SiN film) having a thicknessof 350 nm, an a-Si layer 52′ having a thickness of 30 nm, and a SiN filmhaving a thickness of 120 nm are continuously formed as shown in FIGS.12A and 12B. Then, a channel protection film 48 to serve as an etchingstopper is formed on a self-alignment basis by patterning the samethrough backside exposure. For example, an n⁺a-Si layer having athickness of 30 nm, a Ti layer having a thickness of 20 nm, an aluminumlayer having a thickness of 75 nm, and a Ti layer having a thickness of40 nm are then formed as shown in FIGS. 13A and 13B and are patternedusing the channel protection film 48 as an etching stopper to form drainelectrodes 44, source electrodes 46, and drain bus lines 26. TFTs 42 arecompleted through the above-described steps.

Next, as shown in FIGS. 14A and 14B, for example, a red resist having aphotosensitive pigment dispersed therein is applied to a thickness of3.0 μm and patterned. Thereafter, post-baking is performed to form resinCF layers R in predetermined pixel regions, the layers having contactholes 50 formed above the source electrodes 46.

Next, as shown in FIGS. 15A and 15B, for example, a blue resist having aphotosensitive pigment dispersed therein is applied to a thickness of3.0 μm and patterned. Thereafter, post-baking is performed to form resinCF layers B in predetermined pixel regions. Similarly, as shown in FIGS.16A and 16B, resin CF layers G are formed in predetermined pixelregions. Next, an ITO film having a thickness of 70 nm for example isformed on the entire surface and patterned to form pixel electrodes 14such that their edges in the horizontal direction in the figures overlapedges of the drain bus lines 26 when viewed in the directionperpendicular to the substrate surfaces. A TFT substrate 8 as shown inFIGS. 9 through 10B is completed through the above-described steps.

While the resin CF layers R, G and B are formed directly on source/drainforming layers such as the drain electrodes 44, source electrodes 46 anddrain bus lines 26 in the present embodiment, a protective film may beformed on the source/drain forming layers and the resin CF layers R, Gand B may be formed on the protective film. Alternatively, a protectivefilm may be formed on the resin CF layers R, G and B, and the pixelelectrodes 14 may be formed on the protective film. Obviously, the TFTs42 and resin CF layers R, G and B may be formed and manufactured usingmaterials and steps other than those described above.

Referring to alignment regulating structures, the slits 20 and finerslits 21 are formed on the TFT substrate 8, and the linear protrusions28 are formed on the common electrode substrate 10 in the presentembodiment. However, they may be used in different combinations. Thepresent embodiment provides effects similar to those achieved with theabove-described first basic configuration.

Embodiment 1-2

A description will now be made with reference to FIGS. 17, 18 and 42 ona substrate for a liquid crystal display according to Embodiment 1-2 anda liquid crystal display having the same. FIG. 17 is a sectional view ofthe liquid crystal display of the present embodiment showing aconfiguration thereof, FIG. 17 showing a section similar to that shownin FIG. 8. As shown in FIG. 17, the liquid crystal display of thepresent embodiment has dielectric layers 56 which are formed above slits20 in a TFT substrate 8 and which serve as alignment regulatingstructures for improving response characteristics of liquid crystalmolecules to half tones. The dielectric layers 56 are formed from aphotoresist or the like.

FIG. 18 is a sectional view of the liquid crystal display of the presentembodiment showing a configuration of the same, FIG. 18 showing asection similar to that shown in FIG. 4. As shown in FIG. 18, in theliquid crystal display of the present embodiment, resin CF layers R, Band G are formed in the same order in the vicinity of intersectionsbetween gate bus lines 25 and drain bus lines 26 on the TFT substrate 8.A protrusion 29 which does not function as an alignment regulatingstructure is formed on a common electrode 18 on a common electrodesubstrate 10. A columnar spacer 30 for maintaining a cell gap is formedby a gate bus line 25 on the TFT substrate 8, an insulation film 24, adrain bus line 26, resin CF layers R, G and B, and the protrusion 29 onthe common electrode substrate 10.

The columnar spacer 30 is not limited to the above-describedconfiguration and may be constituted by other layers. For example, it ispossible to use a resin layer that is formed simultaneously with thedielectric layers 56 on the resin CF layer B from the same material asthat of the layers 56. In this case, it is not necessary to form theprotrusion 29 on the common electrode substrate 10. The TFTs 42, resinCF layers R, G and B, and so on may be formed and manufactured usingmaterials and steps other than those described above. The alignmentregulating structures respectively formed on the TFT substrate 8 andcommon electrode substrate 10 may be in other combinations. The presentembodiment provides the same effects as those achieved with theabove-described second basic configuration.

FIG. 42 is a sectional view of the liquid crystal display of the presentembodiment showing a modification of the same, and FIG. 42 shows asection similar to that shown in FIG. 4. As shown in FIG. 42, in theliquid crystal display of the present modification, a columnar spacer 30is structured by only resin CF layers R, B and G laminated in the sameorder in the vicinity of intersections between gate bus lines 25 anddrain bus lines 26 on the TFT substrate 8. Thus, the columnar spacer 30may be formed using neither the protrusion 29 on the common electrodesubstrate 10 nor the dielectric layers 56 on the TFT substrate 8.

It is desirable for the CF-on-TFT structured MVA-LCD having anotheralignment regulation structure besides the protrusion 29 to use thisstructure. In the TN mode LCD, for example, it is necessary to considerthe laminating accuracy at the time of laminating the resin CF layers,the panel attaching accuracy and the necessary area for obtaining theenough height of the layer while the columnar spacer is formed bylaminating the resin CF layers. It is necessary to enlarge the sectionalarea of resin CF layers for forming the columnar spacer, therefore, theproblem that the aperture ratio of pixel has to decrease is caused tothe TN mode LCD.

On the other hand, there is no need to consider the panel attachingaccuracy in the CF-on-TFT structure. However, the aperture ratio ofpixel is decreased by forming the BM layer to shade the defectivealignment of the liquid crystal in the vicinity of columnar spacer.

On the contrary, since the CF-on-TFT structured MVA-LCD has a normallyblack mode which always becomes black on the part of the display wherethe pixel electrode does not exist, there is no need to form BM layers.Therefore, it is possible to suppress the decreasing of aperture ratioof pixel. Moreover, since it is no need to consider the panel attachingaccuracy and the defective alignment of the liquid-crystal in thevicinity of columnar spacer, it is possible to form the columnar spacerwith suppressing the decreasing of aperture ratio of pixel.

Embodiment 1-3

A description will now be made with reference to FIGS. 19 through 22 ona substrate for a liquid crystal display according to Embodiment 1-3, aliquid crystal display having the same, and a method of manufacturingthe same. FIG. 19 shows a configuration of the substrate for a liquidcrystal display of the present embodiment and corresponds to FIG. 6A.FIG. 20 shows a section of the substrate for a liquid crystal displaytaken along the line G-G in FIG. 19 and corresponds to FIG. 6B. As shownin FIGS. 19 and 20, a common electrode 18 is formed on a glass substrate12 in a display area 38 and a frame region 40 on a common electrodesubstrate 10. Linear protrusions 28 are formed on the common electrode18 in the display area 38 at an angle to edges of the display area 38.The linear protrusions 28 are formed by a bottom layer made of chromium(Cr) that is a light-blocking metal and a top layer which is a resistlayer used for patterning Cr. A frame pattern 34 for shielding edges ofthe display area 38 from light is formed in the frame region 40. Across-shaped alignment mark 36 used for combining the common electrodesubstrate with a TFT substrate 8 (which is not shown in FIGS. 19 and 20)in a face-to-face relationship is formed on the glass substrate 10 onthe left side of the frame region 40 in the figure. The frame pattern 34and alignment mark 36 are formed simultaneously with the linearprotrusions 28 from the same material.

A method of manufacturing the substrate for a liquid crystal display ofthe present embodiment will now be described with reference to FIGS. 21and 22. For example, an ITO film having a thickness of 100 nm is firstformed on an entire surface of the glass substrate 12 and patterned asshown in FIG. 21 to form the common electrode 18. For example, a Cr filmhaving a thickness of 100 nm is then formed on the entire surface asshown in FIG. 22. Next, a resist is applied to the entire surface,exposed, and developed to form a predetermined resist pattern. Then, Cris etched using the resist pattern as an etching mask to form the bottomlayer of the linear protrusions 28, the frame pattern 34, and thealignment mark 36. The resist pattern is then hardened throughpost-baking to form the top layer of the linear protrusions 28. Thecommon electrode substrate 10 of the present embodiment is completedthrough the above-described steps.

While a metal layer capable of blocking light such as Cr is used toshield the frame region 40 from light or to allow the alignment mark 36to be visually recognized and a resist is used to form the linearprotrusions 28 in the present embodiment, the need for a metal layer forblocking light can be eliminated by using a black resist for forming anopaque film as the resist layer as shown in FIGS. 5 through 6B. An MVAtype liquid crystal display is in the normally black mode, and such ablack resist will sufficiently work if it has an OD-value (opticaldensity) on the order of 2.0.

As thus described, the present embodiment makes it possible to provide aliquid crystal display having high luminance and preferable displaycharacteristics.

Second Mode for Carrying Out the Invention

A description will now be made with reference to FIGS. 23 and 24 on asubstrate for a liquid crystal display on a second mode for carrying outthe invention, a liquid crystal display having the same, and a method ofmanufacturing the same.

Color liquid crystal displays are used as monitors and displays ofnotebook PCs, PDAs (personal digital assistants), and the like, andthere are recent demands for further reductions in the weight of suchdisplays. In general, glass substrates occupy a great percentage of theweight of a liquid crystal display compared to other members. Forexample, glass substrates having a thickness of 0.7 mm occupy about 40%of the weight of a liquid crystal display. It is a common and effectiveapproach to reduce the weight of glass substrates in order to reduce theweight of a liquid crystal display.

One means for reducing the weight of a glass is to reduce the thicknessof the same. However, it is difficult to form TFTs and color filters ona thin glass through highly accurate patterning, and a problem arises inthat there is a limit on patterning accuracy. When glass substrateshaving different characteristics are used as a TFT substrate and acommon electrode substrate provided in a face-to-face relationship, aproblem arises in that it is difficult to combine them together becauseof deformation of the substrates attributable to heat or the like.Although the two substrates may be polished to reduce the thicknesses ofthem after the liquid crystal panel is completed, a problem arises inthat the manufacturing cost is increased.

Another method for reducing the weight of substrates is to use plasticsubstrates instead of glass substrates. However, this results in thesame problem as encountered in the case of thin glass substrates in thatit is difficult to form TFTs and color filters for which highly accuratepatterning is required. Further, since such substrates are soft, aproblem arises in that they may be insufficient in resistance topressures applied by fingers and the like depending on the intendedusage. It is an object of the present mode for carrying out theinvention to provide a lightweight liquid crystal display having highreliability.

Taking those problems into consideration, in the present mode forcarrying out the invention, TFTs and color filters are formed on onesubstrate. Since this eliminates the need for highly accurate patterningon another substrate, thin glass substrates, plastic substrates or thelike may be freely chosen. Further, columnar spacers for maintaining acell gap are formed on a substrate in advance in the present mode forcarrying out the invention. This makes it possible to provide a stablecell gap and to improve anti-pressure properties.

A more specific description will be made on substrates for a liquidcrystal display in the present mode for carrying out the invention,liquid crystal displays having the same, and methods of manufacturingthe same with reference to Embodiments 2-1 and 2-2.

Embodiment 2-1

A liquid crystal display according to Embodiment 2-1 will now bedescribed. A TFT substrate 8 of the liquid crystal display of thepresent embodiment has a configuration similar to that of the TFTsubstrate 8 in the first mode for carrying out the invention shown inFIGS. 9 through 10B.

FIG. 23 corresponds to FIG. 10A and shows a section of the liquidcrystal display of the present embodiment. As shown in FIG. 23, theliquid crystal display of the present embodiment is formed by combininga TFT substrate 8 and a common electrode substrate 10 having a thicknesssmaller than that of the TFT substrate 8 with a predetermined cell gapkept between them. The common electrode substrate 10 has a commonelectrode 18 formed on a glass substrate 12′ having a thickness smallerthan that of a glass substrate 12 to serve as the TFT substrate 8.

A method of manufacturing a substrate for a liquid crystal displayaccording to the present embodiment and a liquid crystal display havingthe same will now be briefly described. A method of manufacturing theTFT substrate 8 will not be described because it is similar to that inthe first mode for carrying out the invention shown in FIGS. 11A through16B. As shown in FIG. 23, a glass substrate 12′ made of non alkali glasswhich is the same material as that of a glass substrate 12 to serve asthe TFT substrate 8 and which has a thickness smaller than that of theglass substrate 12, e.g., 0.2 mm, is used as the common electrodesubstrate 10. For example, an ITO film having a thickness of 100 nm isformed on an entire surface of the glass substrate 12′ and patterned toform a common electrode 18. This step completes the common electrodesubstrate 10.

Thereafter, alignment films are formed on surfaces of the substrates 8and 10 in a face-to-face relationship and are rubbed. Next, a sealant isapplied, and spacers are dispersed. The substrates 8 and 10 are thencombined and cut into each panel. Next, a liquid crystal is injectedthrough a liquid crystal injection port and sealed, and polarizers areapplied. A liquid crystal display according to the present embodiment iscompleted through the above-described steps.

While non alkali glass having a thickness of 0.2 mm is used as the glasssubstrate 12′ of the present embodiment, glass having a specific densitydifferent from that of the glass substrate 12 may be used instead. Sodalime glass including alkaline components may be used to achieve agreater reduction in the manufacturing cost. For example, the glassincludes 1% or more alkaline components. However, when glass includingalkaline components is used in a liquid crystal display having TFTs 42of the channel-etching type or the like having exposed activesemiconductor layers 52, since the TFTs 42 can be contaminated byalkali, the TFTs 42 are preferably protected with a protective film orthe like. Such a problem will not occur when glass including alkalinecomponents is used in a liquid crystal display having TFTs 42 with achannel protection film.

In the present embodiment, resin CF layers R, G and B are formed on theTFT substrate 8 to allow the use of a substrate made of glass or plasticas the common electrode substrate 10. This makes it possible to providea lightweight and reliable liquid crystal display. Resistance topressures applied by fingers and the like can be improved by providing athicker substrate on the side of the display screen.

Embodiment 2-2

A liquid crystal display according to Embodiment 2-2 will now bedescribed with reference to FIG. 24. FIG. 24 is a sectional view of theliquid crystal display of the present embodiment showing a configurationof the same. As shown in FIG. 24, a common electrode substrate 10 of theliquid crystal display of the present embodiment has a glass substrate12′ having a thickness smaller than that of a glass substrate 12 toserve as a TFT substrate 8 just as in the liquid crystal display ofEmbodiment 2-1.

Resin CF layers B, G and R are formed in the same order on the TFTsubstrate 8, and resin layers 60 made of photosensitive acrylic resinare formed on the same to form columnar spacers 30 for maintaining acell gap. The layers of the columnar spacers 30 may be in otherconfigurations, and the layers may be formed in any order. In the caseof an MVA type liquid crystal display, the resin layers 60 may be formedsimultaneously with linear protrusions as alignment regulatingstructures from the same material as that of the latter.

In the present embodiment, the use of the columnar spacers 30 preventany variation of the cell gap attributable to spherical spacers or thelike dispersed on a substrate surface which can be stranded on alignmentregulating structures, and this makes it possible to provide a stablecell gap. Further, since the columnar spacers 30 are provided on thesubstrate surface uniformly and in a high density, anti-pressureproperties are improved. For this reason, a reliable liquid crystaldisplay can be provided even when the common electrode substrate 10 isprovided on the display screen side. When the TFT substrate 8 isprovided on the display screen side, since reflection is increased bythe metal layer, it is desirable to use a low-reflection multi-layermetal at least on the side of the metal layer facing the glass substrate12.

Effects of the present mode for carrying out the invention will now bespecifically described in comparison to those of a conventional liquidcrystal display. Table 1 specifies two substrates A1 and B1 that form apart of a conventional liquid crystal display. Resin CF layers R, G andB are formed on the substrate A1, and TFTs 42 are formed on thesubstrate B1. The substrates A1 and B1 are made of NA35 glass. Thesubstrates A1 and B1 have a thickness of 0.7 mm and a density of 2.50g/cm³.

TABLE 1 Components Panel Thickness Density on Weight Material (mm)(g/cm³) Substrates Percentage Substrate NA35 glass 0.7 2.50 CF 1 A1Substrate NA35 glass 0.7 2.50 TFT B1

Table 2 specifies two substrates A2 and B2 that form a part of anotherconventional liquid crystal display. NA35 glass having a density of 2.50g/cm³ is used for both of the substrates A2 and B2 similarly to thesubstrates A1 and B1. After they are combined, each of the substrates A2and B2 is polished to a thickness of 0.5 mm. Resin CF layers R, G and Bare formed on the substrate A2, and TFTs 42 are formed on the substrateB2. Although a reduction in weight has been achieved in the resultantpanel in that it has a weight percentage of 0.71 (hereinafter referredto as “panel weight percentages”) where it is assumed that a liquidcrystal panel obtained by combining the substrates A1 and B1 shown inTable 1 has a weight percentage of 1, the panel is more expensivebecause of an increase in the manufacturing cost.

TABLE 2 Components Panel Thickness Density on Weight Material (mm)(g/cm³) Substrates Percentage Substrate NA35 glass 0.5 2.50 CF 0.71 A2Substrate NA35 glass 0.5 2.50 TFT B2

Table 3 specifies two substrates A3 and B3 that form a part of a liquidcrystal display according to the present embodiment. NA35 glass having athickness of 0.7 mm and a density of 2.50 g/cm³ is used for thesubstrate B3 similarly to the substrate B1. TFTs 42 and resin CF layersR, G and B are formed on the substrate B3. Asahi AS glass that is alkaliglass having a thickness of 0.2 mm and a density of 2.49 g/cm³ is usedfor the substrate A3. The resultant panel has a weight percentage of0.64 which represents a weight smaller than that of the panel shown inTable 2. The substrate A3 may be made of any type of glass that islighter than the substrate B3.

TABLE 3 Components Panel Thickness Density on Weight Material (mm)(g/cm³) Substrates Percentage Substrate Asahi AS 0.2 2.49 — 0.64 A3Substrate NA35 glass 0.7 2.50 TFT B3 CF

Table 4 specifies two substrates A4 and B4 that form a part of anotherliquid crystal display according to the present embodiment. NA35 glasshaving a thickness of 0.7 mm and a density of 2.50 g/cm³ is used for thesubstrate B4 similarly to the substrate B1. TFTs and color filters areformed on the substrate B4. Polyethersulfone (PES) having a thickness of0.2 mm and a density of 1.40 g/cm³ is used for the substrate A4. Theresultant panel has a weight percentage of 0.58 which represents agreater reduction in weight than that of the panel shown in Table 3. Thematerial of the substrate A4 is not limited to PES and may be anyplastic such as polycarbonate (PC) or polyacrylate (PAR).

TABLE 4 Components Panel Thickness Density on Weight Material (mm)(g/cm³) Substrates Percentage Substrate PES 0.2 1.40 — 0.58 A4 SubstrateNA35 glass 0.7 2.50 TFT B4 CF

As described above, the resin CF layers R, B and G are formed under thepixel electrodes 14 in the present mode for carrying out the invention.This eliminates any need for highly accurate patterning of the commonelectrode substrate 10 and also eliminates any need for accuratealignment when combining it with the TFT substrate 8. Since this makesit possible to use a glass substrate, plastic substrate, or the likehaving a small thickness as the common electrode substrate 10, alightweight and reliable liquid crystal display can be provided.Further, since there is no need for polishing the TFT substrate 8 andcommon electrode substrate 10 to reduce their thickness after combiningthem, there is no increase in manufacturing steps and manufacturingcost.

Third Mode for Carrying Out the Invention

A description will now be made with reference to FIGS. 25 through 34B ona substrate for a liquid crystal display, a liquid crystal displayhaving the same, and a method of manufacturing the same.

In the case of a substrate for a liquid crystal display having astructure in which resin CF layers R, G and B are formed on a TFTsubstrate 8 (CF-on-TFT structure) as in the first mode for carrying outthe invention, the numerical aperture can be improved because the resinCF layers R, G and B are formed under pixel electrodes 14. This improvesthe transmittance of the panel and makes it possible to improve theluminance of the liquid crystal display.

However, in a substrate for a liquid crystal display having theCF-on-TFT structure as in the first mode for carrying out the invention,if the top of the source/drain metal layers which are the top layer (Agate metal layer may be also included in the top layer in the case of atop gate structure. Hereinafter, such a configuration will be alsosimply referred to as “source/drain metal layers”.) is not covered by aprotective film (passivation film) when the TFTs 42 are formed, thesource/drain metal layers can be corroded by a CF developer when theresin CF layers R, G and B formed above the same are patterned, whichresults in a problem in that the resistance of the bus lines constitutedby the metal layers is increased and in that the bus lines are broken.Another problem arises in that the source electrodes 44 and drainelectrodes 46 are removed as a result of corrosion to expose the activesemiconductor layer 52 which can then be contaminated as a result ofcontact with the CF developer. When a protective film is formed on thesource/drain metal layer using a CVD apparatus, another problem arisesin that there will be an increase in the number of manufacturing steps.It is an object of the present mode for carrying out the invention toprovide a substrate for a liquid crystal display with which aninexpensive and reliable display can be provided, a liquid crystaldisplay having the same, and a method of manufacturing the same.

In the present mode for carrying out the invention, the above-mentionedproblems are solved by covering source/drain metal layers with resin CFlayers R, G and B which are first formed or black matrix resin formedunder the resin CF layers R, G and B or resin that formed a part ofcolumnar spacers 30.

A more specific description will now be made with reference toEmbodiment 3-1 and Embodiment 3-2 on substrates for a liquid crystaldisplay in the present invention, liquid crystal displays having thesame, and methods of manufacturing the same.

Embodiment 3-1

A description will be first made on a substrate for a liquid crystaldisplay according to Embodiment 3-1, a liquid crystal display having thesame, and a method of manufacturing the same with reference to FIGS. 25through 33B. FIG. 25 shows a configuration of the substrate for a liquidcrystal display according to the present embodiment (CF layers areomitted in the figure). FIG. 26A shows a section of the substrate for aliquid crystal display taken along the line J-J in FIG. 25, and FIG. 26Bshows a section of the substrate for a liquid crystal display takenalong the line K-K in FIG. 25. As shown in FIGS. 26A and 26B, in thesubstrate for a liquid crystal display, a black matrix is formed byforming two resin CF layers in different colors at edges of pixelregions. Throughout the black matrix formed by overlapping two resin CFlayers, a resin CF layer R is located at the bottom thereof. The resinCF layers R are formed such that they cover all of source/drain metallayers such as drain bus lines 26. A pixel electrode 14 is formed with aslit 20 extending in parallel with an edge of the pixel region and aplurality of finer slits 21 diagonally extending from the slit 20. Thesubstrate for a liquid crystal display of the present embodiment has aliquid crystal in which a polymeric structure is formed by curingultraviolet monomers through irradiation with ultraviolet light.

A method of manufacturing the substrate for a display of the presentembodiment will now be described with reference to FIGS. 27 through 33B.FIGS. 27 through 30 illustrate a method of manufacturing the substratefor a liquid crystal display of the present embodiment. FIGS. 31Athrough 33B are sectional views at manufacturing steps illustrating themethod of manufacturing the substrate for a liquid crystal display ofthe present embodiment. FIGS. 31A, 32A and 33A show a section similar tothat in FIG. 26A, and FIGS. 31B, 32B and 33B show a section similar tothat in FIG. 26B. Steps up to the formation of TFTs 42 and drain buslines 26 on a glass substrate 12 will not be described because they aresimilar to those in the method of manufacturing the substrate for aliquid crystal display of Embodiment 1-1 shown in FIGS. 11A through 13B.

At steps as shown in FIGS. 11A through 13B, a plurality of gate buslines 25 extending in the horizontal direction in the figures and drainbus lines 26 extending in the vertical direction in the figures acrossthe gate bus lines 25 are formed (see FIG. 27). TFTs 42 are formed inthe vicinity of intersections between the gate bus lines 25 and drainbus lines 26. The gate bus lines 25 and drain bus lines 26 define pixelregions. Storage capacity bus lines (auxiliary capacity electrodes) 62extending through the pixel regions substantially in the middle thereofand substantially in parallel with the gate bus lines 25 are formed inthe same layer as that of the gate bus lines 25. A storage capacityelectrode (intermediate electrode) 64 for each pixel region is formed onthe storage capacity bus line 62 in the same layer as that of the drainbus lines 26.

Next, a photosensitive red resist having a pigment dispersed therein isapplied to a thickness of 1.5 μm f or example and patterned. It isthereafter subjected to post-baking to form first resin CF layers R onpixel regions to display red, the TFTs 42, the gate bus lines 25, thedrain bus lines 26 and the storage capacity bus lines 62 as shown inFIGS. 28, 31A and 31B. At this time, the drain electrodes 44, sourceelectrodes 46 and drain bus lines 26 that are top metal layers arecovered by the resin CF layers R.

Next, a green resist is applied to a thickness of 1.5 μm for example andpatterned. It is thereafter subjected to post-baking to form secondresin CF layers G on pixel regions to display green and on the drain buslines 26 located adjacently to such pixel regions on the left of thesame, as shown in FIGS. 29, 32A and 32B. At this time, a black matrix isformed by overlapping two resin CF layers on the TFTs 42 in the pixelregions, the gate bus lines 25 adjacent to the pixel regions, thestorage capacity bus lines 62 in the pixel regions, and the drain buslines 26 located adjacently to the pixel regions on the left of thesame.

Next, a blue resist is applied to a thickness of 1.5 μm for example andpatterned. It is thereafter subjected to post baking to form third resinCF layers B on pixel regions to display blue, the drain bus lines 26located adjacently to such pixel regions on both sides of the same, andthe TFTs 42 located adjacently to the pixel regions on the right of thesame, as shown in FIGS. 30, 33A and 33B. At this time, a black matrix isformed by overlapping two resin CF layers on the TFTs 42 in the pixelregions located adjacently to the pixel regions on the right of thesame, the gate bus lines 25 adjacent to the pixel regions, the storagecapacity bus lines 62 in the pixel regions, and the drain bus lines 26located adjacently to the pixel regions on both sides of the same.

Thereafter, an ITO film having a thickness of 70 nm for example isformed on the entire surface and patterned to form a pixel electrode 14,a slit 20 and finer slits 21 in each pixel region, which completes asubstrate for a liquid crystal display as shown in FIGS. 25 through 26B.

Next, a vertical alignment film is applied to each of surfaces of acommon electrode substrate formed with a common electrode made of ITOfor example and the above-described substrate for a liquid crystaldisplay, the surfaces facing each other. For example, spherical spacersare then dispersed on one of the substrates, and a sealant is applied tothe periphery of the other substrate. Subsequently, the two substratesare put together, and a liquid crystal is injected into a gap betweenthe substrates. Referring to the liquid crystal, for example, a negativeliquid crystal having negative dielectric anisotropy added with 0.2%ultraviolet-curing monomer by weight may be used. Next, for example, atone voltage of 10 V dc is applied to the drain bus lines 26, and acommon voltage of 5 V dc is applied to the common electrode.Subsequently, for example, a gate voltage of 30 V dc is applied to thegate bus lines 25 to tilt the liquid crystal in the liquid crystal panelwhich is then irradiated with ultraviolet light of 2000 mJ having awavelength in the range from 300 to 450 nm from the opposite substrateside. As a result, the ultraviolet-curing monomers are cured to form apolymeric structure in the liquid crystal in the liquid crystal panel,which causes the liquid crystal molecules (represented by columns in thedrawings) to be tilted in four directions from their states when novoltage is applied, as shown in FIG. 25. In the present embodiment, thepre-tilt angle of the liquid crystal molecules is 86 deg. Thereafter,polarizers are applied to the two substrates to complete the liquidcrystal display of the present embodiment.

Embodiment 3-2

A description will be first made on a substrate for a liquid crystaldisplay according to Embodiment 3-2, a liquid crystal display having thesame, and a method of manufacturing the same with reference to FIGS. 34Aand 34B. FIGS. 34A and 34B are sectional views of the substrate for aliquid crystal display of the present embodiment showing a configurationof the same. While the substrate for a liquid crystal display ofEmbodiment 3-1 has TFTs 42 with a channel protection film, the substratefor a liquid crystal display of the present embodiment haschannel-etched TFTs 66 as shown in FIGS. 34A and 34B.

A description will now be made on a substrate for a liquid crystaldisplay according to the present embodiment, a liquid crystal displayhaving the same, and a method of manufacturing the same. First, forexample, an Al layer having a thickness of 100 nm and a Ti layer havinga thickness of 50 nm are formed in the same order on an entire surfaceof a glass substrate 12 and are patterned to form gate bus lines 25 andstorage capacity bus lines. Next, for example, a SiN film having athickness of 350 nm, an a-Si layer having a thickness of 120 nm, and ann⁺a-Si layer having a thickness of 30 nm are continuously formed. Next,the n⁺a-Si layer and a-Si layer are patterned in the form of islands toform active semiconductor layers 52′ and n-type semiconductor layers(not, shown) located on the same. Next, for example, a MoN film having athickness of 50 nm, an Al film having a thickness of 150 nm, a MoN filmhaving a thickness of 70 nm, and a Mo film having a thickness of 10 nmare continuously formed and patterned, and element isolation is thencarried out to form source electrodes 46, drain electrodes 44, andstorage capacity electrodes. The channel-etched TFTs 66 are completedthrough the above-described steps. Subsequent steps are not illustratedand described because they are similar to those in the method ofmanufacturing the liquid crystal display of Embodiment 3-1 shown inFIGS. 27 through 33B.

A method of manufacturing a substrate for a liquid crystal displayaccording to another embodiment of the invention will now be described.Although not shown, features having the same functions and operations asthose of the features shown in FIGS. 34A and 34B will be described usinglike reference numbers. The substrate for a liquid crystal display ofthe present embodiment has top-gate type TFTs 42. First, for example, aTi layer having a thickness of 20 nm, an Al layer having a thickness of75 nm, a Ti layer having a thickness of 40 nm, and an n⁺a-Si layerhaving a thickness of 30 nm are formed on a glass substrate 12 and arepatterned to form drain electrodes 44 and source electrodes 46. Next,for example, an a-Si layer having a thickness of 30 nm, a SiN filmhaving a thickness of 350 nm, and an Al layer having a thickness of 100nm are formed and patterned to form active semiconductor layers 52′, aninsulation film 24, and gate bus lines 25 simultaneously. Thesemiconductor layers 52′, insulation films 24, and gate bus lines 25 maybe sequentially formed instead of forming them simultaneously. Thetop-gate type TFTs 42 are completed through the above-described steps.Although storage capacity bus lines 62 and storage capacity electrodes64 are not formed in the present embodiment, they may be obviouslyformed. Subsequent steps will not be described because they aresubstantially similar to those of the method of manufacturing the liquidcrystal display of Embodiment 3-1 shown in FIGS. 27 through 33B. In thepresent embodiment, since the top metal layer is the gate metal layer,the gate metal layer is coated with the resin CF layer that is formedfirst.

A method of manufacturing a substrate for a liquid crystal displayaccording to still another embodiment of the invention will now bedescribed. Although not shown, features having the same functions andoperations as those of the features shown in FIGS. 34A and 34B will bedescribed using like reference numbers. The substrate for a liquidcrystal display of the present embodiment has TFTs in which polysilicon(p-Si) is used for active semiconductor layers 52. First, for example, aSiN film having a thickness of 50 nm, a SiO₂ film having a thickness of200 nm, and an a-Si layer having a thickness of 40 nm are formed on aglass substrate 12, and the resultant substrate is subjected to a heattreatment in an annealing oven to be dehydrogenized. Next, the a-Silayer is irradiated with a predetermined laser to be crystallized and isthen patterned to form a p-Si layer. Next, for example, a SiO₂ filmhaving a thickness of 110 nm and a AlNd film having a thickness of 300nm are formed and patterned to form insulation films (gate insulationfilms) 24 and gate bus lines 25.

The p-Si layer is then doped with phosphorus (P) ions to form N-typeregions selectively, and the p-Si layer is subsequently doped with boron(B) ions to form P-type regions selectively. Next, for example, a SiO₂film having a thickness of 60 nm and a SiN film having a thickness of370 nm are formed to form an interlayer insulation film. The interlayerinsulation film on the high density impurity regions is then removed toform contact holes. Next, for example, a Ti layer having a thickness of100 nm, an Al layer having a thickness of 200 nm, and a Ti layer havinga thickness of 100 nm are formed and patterned to form drain electrodes44 and source electrodes 46. TFTs 70 in which p-Si is used for activesemiconductor layers are completed through the above-described steps.Although storage capacity bus lines and storage capacity electrodes arenot formed in the present embodiment, it is obviously possible to formstorage capacity bus lines simultaneously with the gate bus lines fromthe same material and to form storage capacity electrodes simultaneouslywith the source and drain electrodes from the same material.

While the top metal layer is covered by the resin CF layer that isformed first in the above-described embodiment, the top metal layer maybe covered by resin to serve as a black matrix or resin to serve as apart of columnar spacers before the resin CF layer is formed. While ablack matrix is formed by laminating two resin CF layers, i.e., thefirst and second resin CF layers or the first and third resin CF layerson the TFTs 42 and bus lines 25, 26, and 62 in the above-describedembodiment, the black matrix may be formed by staking all of the threeresin CF layers. It is not necessary to form the resin CF layers ifblack matrix is formed at a different step.

Further, while the pixel electrodes 14 in the above-described embodimentare formed with the slits 20 and finer slits 21 because the describedexample is a polymer-fixed liquid crystal display, other alignmentregulating structures may be used. While the entire top metal layer iscovered with a resin CF layer in the above-described embodiment, onlyedge portions of the top metal layer may be covered. Obviously, thesubstrate for a liquid crystal display may have a structure which doesnot include the storage capacity bus lines 62 made of the same materialas that of the gate bus lines 25 and the storage capacity electrodes 64made of the same material as that of the source electrodes 44 and drainelectrodes 46.

As described above, in the present mode for carrying out the invention,the source/drain metal layer (a gate metal layer in the case of atop-gate structure) is covered by the resin CF layer that is formedfirst. This prevents the source/drain layer from being corroded by a CFdeveloper when the resin CF layers are patterned. Since this preventsany increase in the bus line resistance and breakage of the bus lines,an improved yield of manufacture can be achieved. Further, the activesemiconductor layers 52 will not be contaminated. There is no increasein the number of manufacturing steps because it is not necessary to forma protective film on the source/drain metal layer.

The liquid crystal display in the present mode for carrying out theinvention is free from any reduction or irregularity of luminanceattributable to a reduction in retention and burning of patterns. Sincethe resin CF layers R, G and B formed on the TFTs 42 absorb ultravioletlight applied to form a polymeric structure, there will be no displaydefect such as cross-talk or a flicker which is otherwise caused byabnormality in the characteristics of the TFTs 42.

Since the alignment of liquid crystal molecules is separated in fourdirections in the liquid crystal display in the present mode forcarrying out the invention, a wide viewing angle is provided, and highcontrast can be achieved by vertical alignment. Further, since thetilting direction of liquid crystal molecules is regulated by apolymeric structure, high speed response can be achieved.

The invention is not limited to the above-described modes for carryingout the same may be modified in various ways.

For example, the pixel electrodes 14 are formed directly on the resin CFlayers R, G and B in the above-described modes for carrying out theinvention. The invention is not limited to such a configuration, and aprotective film made of an organic or inorganic material may be formedon the resin CF layers R, G and B, and the pixel electrodes 14 maybeformed on the protective film. The formation of such a protective filmmakes it possible to prevent the liquid crystal from being contaminatedby the material of the resin CF layers and to prevent line breakagethrough a reduction in steps at the pixel electrodes 14. The resin CFlayers R, G and B may be formed in any order, and the materials,configurations and thicknesses of the TFTs 42 and resin CF layers R, Gand B are not limited to those described in the above modes for carryingout the invention.

While transmission type liquid crystal displays have been referred to inthe above-described modes for carrying out the invention, the inventionis not limited to them and may be applied to reflection type liquidcrystal displays. While MVA type liquid crystal displays have beenreferred to in the above-described modes for carrying out the invention,the invention is not limited to them and may be applied to liquidcrystal displays in other modes such as the TN mode.

As thus described, the present invention makes it possible to provide aliquid crystal display having high luminance and preferable displaycharacteristics.

1. A liquid crystal display configured to enclose liquid crystalcomprising: a thin film transistor substrate including a firstsubstrate, a plurality of bus lines formed on the first substrate suchthat they intersect each other, pixel regions defined by the bus lines,a thin film transistor formed in each of the pixel regions, a resincolor filter layer formed of a plurality of different color layers andin each of the pixel regions, and a pixel electrode formed in each ofthe pixel regions; a common electrode substrate including a secondsubstrate and a common electrode formed on the second substrate, thecommon electrode substrate being provided in a face-to-face relationshipwith the first substrate; a liquid crystal sealed between the thin filmtransistor substrate and the common electrode substrate; and a columnarspacer having laminated resin layers including the resin color filterlayer and a second resin layer made of photosensitive acrylic resin,both the second resin layer and each of the different color layers beingconfigured to be in contact with the liquid crystal, for maintaining acell gap between the thin film transistor substrate and the commonelectrode substrate, wherein at least surfaces of the bus lines facingthe first substrate are formed from a low reflection material, whereinone of the plurality of bus lines is located directly below the columnarspacer, wherein another of the plurality of bus lines separates a firstresin color filter layer of the resin color filter layer from a secondresin color filter layer of the resin color filter layer thin filmtransistor substrate when viewed in a direction perpendicular to thethin film transistor substrate.
 2. A liquid crystal display according toclaim 1, wherein the second substrate is lighter in weight than thefirst substrate.
 3. A liquid crystal display according to claim 1,wherein the second substrate is formed from a glass material includingalkaline components.
 4. A liquid crystal display according to claim 3,wherein the glass material includes 1% or more alkaline components.
 5. Aliquid crystal display according to claim 1, wherein the secondsubstrate is formed from a resin material.
 6. A liquid crystal displayaccording to claim 1, wherein at least surfaces of a drain electrode anda source electrode of the thin film transistor facing the firstsubstrate are formed from a low reflection material.
 7. A liquid crystaldisplay according to claim 1, wherein the second substrate has athickness smaller than that of the first substrate.
 8. A liquid crystaldisplay according to claim 1, wherein the thin film transistor substrateis located adjacent to a display side.
 9. A liquid crystal displayconfigured to enclose liquid crystal according to claim 1, wherein theresin layer made of photosensitive acrylic resin has a width that isapproximately equal to a width of the resin color filter layer.
 10. Aliquid crystal display configured to enclose liquid crystal according toclaim 1, further comprising an alignment regulating structure forregulating the alignment of the liquid crystal, wherein the resin layermade of photosensitive acrylic resin is made from a same material as thealignment regulating structure.
 11. A liquid crystal display accordingto claim 1, wherein the one bus line located directly below the columnarspacer has a side extending between the thin film transistor substrateand the common electrode substrate, the side at an intersection ofdifferent color layers of the color filter layer when viewed in thedirection perpendicular to the thin film transistor substrate.